Journal of Environment and Earth Science www.iiste.org ISSN 2224-3216 (Paper) ISSN 2225-0948 (Online) Vol. 3, No.12, 2013 33 ASTER VNIR & SWIR Band Enhancement for Lithological Mapping - A case study of the Azegour Area (Western High Atlas, Morocco) Mouhssine WAHI 1* ; Kamal TAJ-EDDINE 1 ; Noureddine LAFTOUHI 2 1. DYBAGEO Laboratory, Department of Geology, Faculty of Sciences SEMLALIA - Cadi Ayyad University, Prince Moulay Abdellah Boulevard, P.O. Box 2390, 40 000 Marrakech, Morocco. 2. GEOHYD Laboratory, Department of Geology, Faculty of Sciences SEMLALIA - Cadi Ayyad University, P.O. Box 2390 Marrakech, Morocco. * E-mail of the corresponding author: mouhssine.wahi@gmail.com Abstract The purpose of this study is to emphasize on the ASTER images effectiveness and capabilities in the field of lithological mapping. An ASTER image (L1b) covering the study area has been used. Visible, near-infrared and short wave infrared reflectance data (9 ASTER bands) have been processed and interpreted. Preprocessing included geometric correction; crossTalk correction; orthorectification. Then the VNIR and SWIR bands have been normalized using the Flat Field Calibration method. Digital processing focused on image enhancement by applying principal component analysis (PCA) and a minimum noise fraction (MNF) transformation. This was achieved by using ENVI 4.7®. Results showed that there are dissimilarities with the published geological map. Offset between lithological boundaries and the obtained results, textures and/or contrast detected inside homogeneously mapped layers have been observed. The existing geological map contains relevant lithological information, however these results provide a new layer of information that can be used to upgrade it. Thus the image enhancement of ASTER remote sensing data can be used as a powerful tool for lithological mapping. Keywords: ASTER, Lithological Mapping, Band enhancement, Western High Atlas, 1. Introduction A geological map is a representation of an outcropping pattern on the surface of the ground. This pattern may indicate bed rocks or the regolith (indicating the altered part of the bed rock and including the surface formations). A geological map contains information about the limits of the outcropping features, the rock units or the geologic strata. Geological maps can provide the basis for exploring the landmass in search of its resources. The Time, accessibility and heterogeneity of the information which is added to the empirical means of extrapolation and interpolation used for mapping makes the usual mapping methods long, hard and expensive. To mitigate these problems, the use of remote sensing data can constitute a considerable information source. Actually, geological features on the surface may be distinguishable in bedrock outcroppings, from air photographs (photogeological reconnaissance) and/or from satellite images. In fact, each sensor measures the physical properties of land surface with precise characteristics (spatial, spectral and radiometric resolutions, viewing angle, acquisition time…). The use of remote sensing data can provide digital and georeferenced information which can be used in geological mapping. Many earlier studies have suggested several methodologies for lithological discrimination and mapping of surface features by using multispectral or/and hyperspectral remote sensing. (Rencz, 1999). This study aims to provide an overview of the use of remote sensing data more specifically ASTER images, in the field of geological mapping in the region of AZEGOUR (Occidental High Atlas, MOROCCO). This will be achieved mainly using digital processing, particularly, principal component analysis (PCA) and minimum noise fraction (MNF) in order to enhance the capability of lithological discrimination between different rock units in the study area. 2. General characteristics of the study area 2.1. Study area location The study area is located on the Northern slope of the Western High Atlas, at 60km to the SSW of the city of Marrakech (Figure 1). The Western High Atlas rises from the Atlantic coast until the highest segment of the chain (High Atlas of Marrakech). It’s the oldest massif of the High Atlas chain, constituted of Paleozoic and post Paleozoic formations. Its highest peak is Jbel Toubkal (4167 meters). Two orogenies have affected this area: The Hercynian orogeny marked by synschistose folds with an overall direction N-S and assigned to the post- visean phase of regional deformation (Lagarde, 1987), and the Atlasic orogeny, less intense than the previous one,